Department of Agronomy
North Dakota State University
Fargo, North Dakota, 58105. U.S.A.
Plant height or culm length in barley is controlled by an array of minor and major factors. Genes which normally cause small changes in plant height are important because they may interact differently with factors which have a pronounced effect on culm length. In addition to naturally occurring plant height genes, numerous induced plant height mutants have been reported. Analyses of mutants indicate that semi-dwarf genes have very specific effects on culm and rachis internode elongation when evaluated in a given environment and one genetic background (4, 5). In other environments and genotypes, however, the expression of major genes is frequently altered (1, 2). Even alleles at the same locus may control an array of changes in plant height (3, 5).
A collection of plant height mutants is being established at North Dakota State University to preserve semi-dwarf genes in order to facilitate their utilization in barley improvement programs and to expand the genetic resources of barley. The base collection will contain mutants and lines in which a significant reduction in plant height has been reported. Each entry will be assigned a Dwarf Stock (DWS) number and will be maintained in its original genetic background.
From the base collection, a working collection of semi-dwarf genes will be developed to maintain specific genes in a common genetic background. Prior to adding new genes in the working collection, information allelism or map location will be needed. A semi-dwarf gene placed in the working collection will be assigned a Genetic Dwarf (GD) number. To facilitate genetic studies, Dr. T. Tsuchiya has suggested that the msg for male-sterility be added to each GD line.
To expand the base collection, I will need assistance from all barley workers. Many researchers have induced plant height mutants in barley using various mutagenic agents. Each event may be an unique modification of the barley genome. I request that workers who have access to such mutants send me a few seeds of each line for inclusion in the base collection of semi-dwarf mutants.
Since semi-dwarf genes commonly have pleiotropic effects on many plant characteristics, a large number of mutant types must be included in the base collection. Traits affected by various semi-dwarf mutants include culm length and thickness, awn length, rachis internode length and number, kernel shape, leaf blade shape and size, coleoptile length and shape, tiller number, coiling of plant parts and male fertility. Since various authors consider different morphological traits as primary and secondary effects of a given mutant, many gene symbols have been assigned to plant height genes: ari, br, cu, cud, dwf, glo, h, lin, mnd, mo, l, lzd, nld, rnt, sid, sdw, sld, uz and wnd. Allelism test among gene assigned different gene symbols suggest that at least a few of them are alleles (6, 7).